The eye produces tears which are spread across the eye during blinking. The unique components of tears along with the blinking process create a tear film that is made up of a mucous layer, an aqueous layer and a lipid layer. This tear film evaporates, drains and is replaced by new tear film components during blinking. This unique system creates a barrier between the environment and the surface of the eye and removes any irritants that may enter the eye.
Dry eye is a common affliction that is caused by the failure of the eye to produce either an adequate amount or maintain a proper balance of tear components. In either instance the tear film that normally covers the eye becomes unstable (i.e. no longer covers the entire eye) and fails to remove irritants. These irritants cause many of the conditions associated with dry eye such as burning, stinging, itching and tired eyes. Dry eye symptoms can be exacerbated by activities that extend the time between eye blinks such as prolonged computer use and reading.
Artificial tear compositions contain polymers that act to mimic the aqueous, mucous and/or lipid layers of the tear film to maintain the stability of the film and prevent rapid evaporation. High viscosity compositions maintain a longer lasting tear film but are difficult to apply and can result in blurred vision. Low viscosity compositions do not maintain a long lasting tear film, in part, due to forces applied during blinking. Normally, blinking causes a shear force to be applied to the tear film, spreading the new tear components across the eye. This same shear force aids in the evaporation and drainage of the existing tear components. When natural tear components are being supplemented by artificial tears, repeated application of the artificial tears is necessary to replace those components that are lost due to blinking. The viscosity of the artificial tear composition has a direct correlation with the ability to withstand the shear force caused by blinking.
Currently available artificial tear compositions are deficient because they either maintain a stable tear film for a short period of time or cause blurred vision for a relatively long period of time. The longest lasting artificial tears on the market use high concentrations of viscosity enhancing agents. Celluvisc° (Celluvisc is a registered trademark of Allergan, Inc.), which uses high viscosity carboxymethyl cellulose (“CMC”) 1%—about 350 centipoise (cps) viscosity, and Refresh Liquigel° (Refresh Liquigel is a registered trademark of Allergan, Inc.), which uses a blend of 0.35% high viscosity CMC and 0.65% low viscosity CMC—about 70 cps, are two such compositions. These high viscosity artificial tear compositions are long lasting but cause significantly blurred vision lasting up to 10 minutes or longer.
There is a need in the art for a long-lasting artificial tear composition that is comfortable to the user and causes a relatively short period of blurred vision upon instillation.
Additionally, there exist products on the market for cleaning contact lenses once removed from the eye. However, there is no product on the market that cleans the contact lens while in the eye. There remains a need for such a product to reduce build up and clean contact lenses while in the eye.